<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    //声明一个对象
    let s = {
      name: '张三',
      add(key){
        this[key] = 'xxx';
        return this;
      }
    }
    
    let result = s.add('age');




  </script>
</body>
</html>